Merge branch 'jt/fetch-large-handshake-window-on-http'
[git] / daemon.c
1 #include "cache.h"
2 #include "pkt-line.h"
3 #include "run-command.h"
4 #include "strbuf.h"
5 #include "string-list.h"
6
7 #ifndef HOST_NAME_MAX
8 #define HOST_NAME_MAX 256
9 #endif
10
11 #ifdef NO_INITGROUPS
12 #define initgroups(x, y) (0) /* nothing */
13 #endif
14
15 static int log_syslog;
16 static int verbose;
17 static int reuseaddr;
18 static int informative_errors;
19
20 static const char daemon_usage[] =
21 "git daemon [--verbose] [--syslog] [--export-all]\n"
22 "           [--timeout=<n>] [--init-timeout=<n>] [--max-connections=<n>]\n"
23 "           [--strict-paths] [--base-path=<path>] [--base-path-relaxed]\n"
24 "           [--user-path | --user-path=<path>]\n"
25 "           [--interpolated-path=<path>]\n"
26 "           [--reuseaddr] [--pid-file=<file>]\n"
27 "           [--(enable|disable|allow-override|forbid-override)=<service>]\n"
28 "           [--access-hook=<path>]\n"
29 "           [--inetd | [--listen=<host_or_ipaddr>] [--port=<n>]\n"
30 "                      [--detach] [--user=<user> [--group=<group>]]\n"
31 "           [<directory>...]";
32
33 /* List of acceptable pathname prefixes */
34 static const char **ok_paths;
35 static int strict_paths;
36
37 /* If this is set, git-daemon-export-ok is not required */
38 static int export_all_trees;
39
40 /* Take all paths relative to this one if non-NULL */
41 static const char *base_path;
42 static const char *interpolated_path;
43 static int base_path_relaxed;
44
45 /* If defined, ~user notation is allowed and the string is inserted
46  * after ~user/.  E.g. a request to git://host/~alice/frotz would
47  * go to /home/alice/pub_git/frotz with --user-path=pub_git.
48  */
49 static const char *user_path;
50
51 /* Timeout, and initial timeout */
52 static unsigned int timeout;
53 static unsigned int init_timeout;
54
55 struct hostinfo {
56         struct strbuf hostname;
57         struct strbuf canon_hostname;
58         struct strbuf ip_address;
59         struct strbuf tcp_port;
60         unsigned int hostname_lookup_done:1;
61         unsigned int saw_extended_args:1;
62 };
63
64 static void lookup_hostname(struct hostinfo *hi);
65
66 static const char *get_canon_hostname(struct hostinfo *hi)
67 {
68         lookup_hostname(hi);
69         return hi->canon_hostname.buf;
70 }
71
72 static const char *get_ip_address(struct hostinfo *hi)
73 {
74         lookup_hostname(hi);
75         return hi->ip_address.buf;
76 }
77
78 static void logreport(int priority, const char *err, va_list params)
79 {
80         if (log_syslog) {
81                 char buf[1024];
82                 vsnprintf(buf, sizeof(buf), err, params);
83                 syslog(priority, "%s", buf);
84         } else {
85                 /*
86                  * Since stderr is set to buffered mode, the
87                  * logging of different processes will not overlap
88                  * unless they overflow the (rather big) buffers.
89                  */
90                 fprintf(stderr, "[%"PRIuMAX"] ", (uintmax_t)getpid());
91                 vfprintf(stderr, err, params);
92                 fputc('\n', stderr);
93                 fflush(stderr);
94         }
95 }
96
97 __attribute__((format (printf, 1, 2)))
98 static void logerror(const char *err, ...)
99 {
100         va_list params;
101         va_start(params, err);
102         logreport(LOG_ERR, err, params);
103         va_end(params);
104 }
105
106 __attribute__((format (printf, 1, 2)))
107 static void loginfo(const char *err, ...)
108 {
109         va_list params;
110         if (!verbose)
111                 return;
112         va_start(params, err);
113         logreport(LOG_INFO, err, params);
114         va_end(params);
115 }
116
117 static void NORETURN daemon_die(const char *err, va_list params)
118 {
119         logreport(LOG_ERR, err, params);
120         exit(1);
121 }
122
123 struct expand_path_context {
124         const char *directory;
125         struct hostinfo *hostinfo;
126 };
127
128 static size_t expand_path(struct strbuf *sb, const char *placeholder, void *ctx)
129 {
130         struct expand_path_context *context = ctx;
131         struct hostinfo *hi = context->hostinfo;
132
133         switch (placeholder[0]) {
134         case 'H':
135                 strbuf_addbuf(sb, &hi->hostname);
136                 return 1;
137         case 'C':
138                 if (placeholder[1] == 'H') {
139                         strbuf_addstr(sb, get_canon_hostname(hi));
140                         return 2;
141                 }
142                 break;
143         case 'I':
144                 if (placeholder[1] == 'P') {
145                         strbuf_addstr(sb, get_ip_address(hi));
146                         return 2;
147                 }
148                 break;
149         case 'P':
150                 strbuf_addbuf(sb, &hi->tcp_port);
151                 return 1;
152         case 'D':
153                 strbuf_addstr(sb, context->directory);
154                 return 1;
155         }
156         return 0;
157 }
158
159 static const char *path_ok(const char *directory, struct hostinfo *hi)
160 {
161         static char rpath[PATH_MAX];
162         static char interp_path[PATH_MAX];
163         const char *path;
164         const char *dir;
165
166         dir = directory;
167
168         if (daemon_avoid_alias(dir)) {
169                 logerror("'%s': aliased", dir);
170                 return NULL;
171         }
172
173         if (*dir == '~') {
174                 if (!user_path) {
175                         logerror("'%s': User-path not allowed", dir);
176                         return NULL;
177                 }
178                 if (*user_path) {
179                         /* Got either "~alice" or "~alice/foo";
180                          * rewrite them to "~alice/%s" or
181                          * "~alice/%s/foo".
182                          */
183                         int namlen, restlen = strlen(dir);
184                         const char *slash = strchr(dir, '/');
185                         if (!slash)
186                                 slash = dir + restlen;
187                         namlen = slash - dir;
188                         restlen -= namlen;
189                         loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
190                         snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
191                                  namlen, dir, user_path, restlen, slash);
192                         dir = rpath;
193                 }
194         }
195         else if (interpolated_path && hi->saw_extended_args) {
196                 struct strbuf expanded_path = STRBUF_INIT;
197                 struct expand_path_context context;
198
199                 context.directory = directory;
200                 context.hostinfo = hi;
201
202                 if (*dir != '/') {
203                         /* Allow only absolute */
204                         logerror("'%s': Non-absolute path denied (interpolated-path active)", dir);
205                         return NULL;
206                 }
207
208                 strbuf_expand(&expanded_path, interpolated_path,
209                               expand_path, &context);
210                 strlcpy(interp_path, expanded_path.buf, PATH_MAX);
211                 strbuf_release(&expanded_path);
212                 loginfo("Interpolated dir '%s'", interp_path);
213
214                 dir = interp_path;
215         }
216         else if (base_path) {
217                 if (*dir != '/') {
218                         /* Allow only absolute */
219                         logerror("'%s': Non-absolute path denied (base-path active)", dir);
220                         return NULL;
221                 }
222                 snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
223                 dir = rpath;
224         }
225
226         path = enter_repo(dir, strict_paths);
227         if (!path && base_path && base_path_relaxed) {
228                 /*
229                  * if we fail and base_path_relaxed is enabled, try without
230                  * prefixing the base path
231                  */
232                 dir = directory;
233                 path = enter_repo(dir, strict_paths);
234         }
235
236         if (!path) {
237                 logerror("'%s' does not appear to be a git repository", dir);
238                 return NULL;
239         }
240
241         if ( ok_paths && *ok_paths ) {
242                 const char **pp;
243                 int pathlen = strlen(path);
244
245                 /* The validation is done on the paths after enter_repo
246                  * appends optional {.git,.git/.git} and friends, but
247                  * it does not use getcwd().  So if your /pub is
248                  * a symlink to /mnt/pub, you can whitelist /pub and
249                  * do not have to say /mnt/pub.
250                  * Do not say /pub/.
251                  */
252                 for ( pp = ok_paths ; *pp ; pp++ ) {
253                         int len = strlen(*pp);
254                         if (len <= pathlen &&
255                             !memcmp(*pp, path, len) &&
256                             (path[len] == '\0' ||
257                              (!strict_paths && path[len] == '/')))
258                                 return path;
259                 }
260         }
261         else {
262                 /* be backwards compatible */
263                 if (!strict_paths)
264                         return path;
265         }
266
267         logerror("'%s': not in whitelist", path);
268         return NULL;            /* Fallthrough. Deny by default */
269 }
270
271 typedef int (*daemon_service_fn)(void);
272 struct daemon_service {
273         const char *name;
274         const char *config_name;
275         daemon_service_fn fn;
276         int enabled;
277         int overridable;
278 };
279
280 static int daemon_error(const char *dir, const char *msg)
281 {
282         if (!informative_errors)
283                 msg = "access denied or repository not exported";
284         packet_write(1, "ERR %s: %s", msg, dir);
285         return -1;
286 }
287
288 static const char *access_hook;
289
290 static int run_access_hook(struct daemon_service *service, const char *dir,
291                            const char *path, struct hostinfo *hi)
292 {
293         struct child_process child = CHILD_PROCESS_INIT;
294         struct strbuf buf = STRBUF_INIT;
295         const char *argv[8];
296         const char **arg = argv;
297         char *eol;
298         int seen_errors = 0;
299
300         *arg++ = access_hook;
301         *arg++ = service->name;
302         *arg++ = path;
303         *arg++ = hi->hostname.buf;
304         *arg++ = get_canon_hostname(hi);
305         *arg++ = get_ip_address(hi);
306         *arg++ = hi->tcp_port.buf;
307         *arg = NULL;
308
309         child.use_shell = 1;
310         child.argv = argv;
311         child.no_stdin = 1;
312         child.no_stderr = 1;
313         child.out = -1;
314         if (start_command(&child)) {
315                 logerror("daemon access hook '%s' failed to start",
316                          access_hook);
317                 goto error_return;
318         }
319         if (strbuf_read(&buf, child.out, 0) < 0) {
320                 logerror("failed to read from pipe to daemon access hook '%s'",
321                          access_hook);
322                 strbuf_reset(&buf);
323                 seen_errors = 1;
324         }
325         if (close(child.out) < 0) {
326                 logerror("failed to close pipe to daemon access hook '%s'",
327                          access_hook);
328                 seen_errors = 1;
329         }
330         if (finish_command(&child))
331                 seen_errors = 1;
332
333         if (!seen_errors) {
334                 strbuf_release(&buf);
335                 return 0;
336         }
337
338 error_return:
339         strbuf_ltrim(&buf);
340         if (!buf.len)
341                 strbuf_addstr(&buf, "service rejected");
342         eol = strchr(buf.buf, '\n');
343         if (eol)
344                 *eol = '\0';
345         errno = EACCES;
346         daemon_error(dir, buf.buf);
347         strbuf_release(&buf);
348         return -1;
349 }
350
351 static int run_service(const char *dir, struct daemon_service *service,
352                        struct hostinfo *hi)
353 {
354         const char *path;
355         int enabled = service->enabled;
356         struct strbuf var = STRBUF_INIT;
357
358         loginfo("Request %s for '%s'", service->name, dir);
359
360         if (!enabled && !service->overridable) {
361                 logerror("'%s': service not enabled.", service->name);
362                 errno = EACCES;
363                 return daemon_error(dir, "service not enabled");
364         }
365
366         if (!(path = path_ok(dir, hi)))
367                 return daemon_error(dir, "no such repository");
368
369         /*
370          * Security on the cheap.
371          *
372          * We want a readable HEAD, usable "objects" directory, and
373          * a "git-daemon-export-ok" flag that says that the other side
374          * is ok with us doing this.
375          *
376          * path_ok() uses enter_repo() and does whitelist checking.
377          * We only need to make sure the repository is exported.
378          */
379
380         if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
381                 logerror("'%s': repository not exported.", path);
382                 errno = EACCES;
383                 return daemon_error(dir, "repository not exported");
384         }
385
386         if (service->overridable) {
387                 strbuf_addf(&var, "daemon.%s", service->config_name);
388                 git_config_get_bool(var.buf, &enabled);
389                 strbuf_release(&var);
390         }
391         if (!enabled) {
392                 logerror("'%s': service not enabled for '%s'",
393                          service->name, path);
394                 errno = EACCES;
395                 return daemon_error(dir, "service not enabled");
396         }
397
398         /*
399          * Optionally, a hook can choose to deny access to the
400          * repository depending on the phase of the moon.
401          */
402         if (access_hook && run_access_hook(service, dir, path, hi))
403                 return -1;
404
405         /*
406          * We'll ignore SIGTERM from now on, we have a
407          * good client.
408          */
409         signal(SIGTERM, SIG_IGN);
410
411         return service->fn();
412 }
413
414 static void copy_to_log(int fd)
415 {
416         struct strbuf line = STRBUF_INIT;
417         FILE *fp;
418
419         fp = fdopen(fd, "r");
420         if (fp == NULL) {
421                 logerror("fdopen of error channel failed");
422                 close(fd);
423                 return;
424         }
425
426         while (strbuf_getline_lf(&line, fp) != EOF) {
427                 logerror("%s", line.buf);
428                 strbuf_setlen(&line, 0);
429         }
430
431         strbuf_release(&line);
432         fclose(fp);
433 }
434
435 static int run_service_command(const char **argv)
436 {
437         struct child_process cld = CHILD_PROCESS_INIT;
438
439         cld.argv = argv;
440         cld.git_cmd = 1;
441         cld.err = -1;
442         if (start_command(&cld))
443                 return -1;
444
445         close(0);
446         close(1);
447
448         copy_to_log(cld.err);
449
450         return finish_command(&cld);
451 }
452
453 static int upload_pack(void)
454 {
455         /* Timeout as string */
456         char timeout_buf[64];
457         const char *argv[] = { "upload-pack", "--strict", NULL, ".", NULL };
458
459         argv[2] = timeout_buf;
460
461         snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);
462         return run_service_command(argv);
463 }
464
465 static int upload_archive(void)
466 {
467         static const char *argv[] = { "upload-archive", ".", NULL };
468         return run_service_command(argv);
469 }
470
471 static int receive_pack(void)
472 {
473         static const char *argv[] = { "receive-pack", ".", NULL };
474         return run_service_command(argv);
475 }
476
477 static struct daemon_service daemon_service[] = {
478         { "upload-archive", "uploadarch", upload_archive, 0, 1 },
479         { "upload-pack", "uploadpack", upload_pack, 1, 1 },
480         { "receive-pack", "receivepack", receive_pack, 0, 1 },
481 };
482
483 static void enable_service(const char *name, int ena)
484 {
485         int i;
486         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
487                 if (!strcmp(daemon_service[i].name, name)) {
488                         daemon_service[i].enabled = ena;
489                         return;
490                 }
491         }
492         die("No such service %s", name);
493 }
494
495 static void make_service_overridable(const char *name, int ena)
496 {
497         int i;
498         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
499                 if (!strcmp(daemon_service[i].name, name)) {
500                         daemon_service[i].overridable = ena;
501                         return;
502                 }
503         }
504         die("No such service %s", name);
505 }
506
507 static void parse_host_and_port(char *hostport, char **host,
508         char **port)
509 {
510         if (*hostport == '[') {
511                 char *end;
512
513                 end = strchr(hostport, ']');
514                 if (!end)
515                         die("Invalid request ('[' without ']')");
516                 *end = '\0';
517                 *host = hostport + 1;
518                 if (!end[1])
519                         *port = NULL;
520                 else if (end[1] == ':')
521                         *port = end + 2;
522                 else
523                         die("Garbage after end of host part");
524         } else {
525                 *host = hostport;
526                 *port = strrchr(hostport, ':');
527                 if (*port) {
528                         **port = '\0';
529                         ++*port;
530                 }
531         }
532 }
533
534 /*
535  * Sanitize a string from the client so that it's OK to be inserted into a
536  * filesystem path. Specifically, we disallow slashes, runs of "..", and
537  * trailing and leading dots, which means that the client cannot escape
538  * our base path via ".." traversal.
539  */
540 static void sanitize_client(struct strbuf *out, const char *in)
541 {
542         for (; *in; in++) {
543                 if (*in == '/')
544                         continue;
545                 if (*in == '.' && (!out->len || out->buf[out->len - 1] == '.'))
546                         continue;
547                 strbuf_addch(out, *in);
548         }
549
550         while (out->len && out->buf[out->len - 1] == '.')
551                 strbuf_setlen(out, out->len - 1);
552 }
553
554 /*
555  * Like sanitize_client, but we also perform any canonicalization
556  * to make life easier on the admin.
557  */
558 static void canonicalize_client(struct strbuf *out, const char *in)
559 {
560         sanitize_client(out, in);
561         strbuf_tolower(out);
562 }
563
564 /*
565  * Read the host as supplied by the client connection.
566  */
567 static void parse_host_arg(struct hostinfo *hi, char *extra_args, int buflen)
568 {
569         char *val;
570         int vallen;
571         char *end = extra_args + buflen;
572
573         if (extra_args < end && *extra_args) {
574                 hi->saw_extended_args = 1;
575                 if (strncasecmp("host=", extra_args, 5) == 0) {
576                         val = extra_args + 5;
577                         vallen = strlen(val) + 1;
578                         if (*val) {
579                                 /* Split <host>:<port> at colon. */
580                                 char *host;
581                                 char *port;
582                                 parse_host_and_port(val, &host, &port);
583                                 if (port)
584                                         sanitize_client(&hi->tcp_port, port);
585                                 canonicalize_client(&hi->hostname, host);
586                                 hi->hostname_lookup_done = 0;
587                         }
588
589                         /* On to the next one */
590                         extra_args = val + vallen;
591                 }
592                 if (extra_args < end && *extra_args)
593                         die("Invalid request");
594         }
595 }
596
597 /*
598  * Locate canonical hostname and its IP address.
599  */
600 static void lookup_hostname(struct hostinfo *hi)
601 {
602         if (!hi->hostname_lookup_done && hi->hostname.len) {
603 #ifndef NO_IPV6
604                 struct addrinfo hints;
605                 struct addrinfo *ai;
606                 int gai;
607                 static char addrbuf[HOST_NAME_MAX + 1];
608
609                 memset(&hints, 0, sizeof(hints));
610                 hints.ai_flags = AI_CANONNAME;
611
612                 gai = getaddrinfo(hi->hostname.buf, NULL, &hints, &ai);
613                 if (!gai) {
614                         struct sockaddr_in *sin_addr = (void *)ai->ai_addr;
615
616                         inet_ntop(AF_INET, &sin_addr->sin_addr,
617                                   addrbuf, sizeof(addrbuf));
618                         strbuf_addstr(&hi->ip_address, addrbuf);
619
620                         if (ai->ai_canonname)
621                                 sanitize_client(&hi->canon_hostname,
622                                                 ai->ai_canonname);
623                         else
624                                 strbuf_addbuf(&hi->canon_hostname,
625                                               &hi->ip_address);
626
627                         freeaddrinfo(ai);
628                 }
629 #else
630                 struct hostent *hent;
631                 struct sockaddr_in sa;
632                 char **ap;
633                 static char addrbuf[HOST_NAME_MAX + 1];
634
635                 hent = gethostbyname(hi->hostname.buf);
636                 if (hent) {
637                         ap = hent->h_addr_list;
638                         memset(&sa, 0, sizeof sa);
639                         sa.sin_family = hent->h_addrtype;
640                         sa.sin_port = htons(0);
641                         memcpy(&sa.sin_addr, *ap, hent->h_length);
642
643                         inet_ntop(hent->h_addrtype, &sa.sin_addr,
644                                   addrbuf, sizeof(addrbuf));
645
646                         sanitize_client(&hi->canon_hostname, hent->h_name);
647                         strbuf_addstr(&hi->ip_address, addrbuf);
648                 }
649 #endif
650                 hi->hostname_lookup_done = 1;
651         }
652 }
653
654 static void hostinfo_init(struct hostinfo *hi)
655 {
656         memset(hi, 0, sizeof(*hi));
657         strbuf_init(&hi->hostname, 0);
658         strbuf_init(&hi->canon_hostname, 0);
659         strbuf_init(&hi->ip_address, 0);
660         strbuf_init(&hi->tcp_port, 0);
661 }
662
663 static void hostinfo_clear(struct hostinfo *hi)
664 {
665         strbuf_release(&hi->hostname);
666         strbuf_release(&hi->canon_hostname);
667         strbuf_release(&hi->ip_address);
668         strbuf_release(&hi->tcp_port);
669 }
670
671 static void set_keep_alive(int sockfd)
672 {
673         int ka = 1;
674
675         if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &ka, sizeof(ka)) < 0) {
676                 if (errno != ENOTSOCK)
677                         logerror("unable to set SO_KEEPALIVE on socket: %s",
678                                 strerror(errno));
679         }
680 }
681
682 static int execute(void)
683 {
684         char *line = packet_buffer;
685         int pktlen, len, i;
686         char *addr = getenv("REMOTE_ADDR"), *port = getenv("REMOTE_PORT");
687         struct hostinfo hi;
688
689         hostinfo_init(&hi);
690
691         if (addr)
692                 loginfo("Connection from %s:%s", addr, port);
693
694         set_keep_alive(0);
695         alarm(init_timeout ? init_timeout : timeout);
696         pktlen = packet_read(0, NULL, NULL, packet_buffer, sizeof(packet_buffer), 0);
697         alarm(0);
698
699         len = strlen(line);
700         if (pktlen != len)
701                 loginfo("Extended attributes (%d bytes) exist <%.*s>",
702                         (int) pktlen - len,
703                         (int) pktlen - len, line + len + 1);
704         if (len && line[len-1] == '\n') {
705                 line[--len] = 0;
706                 pktlen--;
707         }
708
709         if (len != pktlen)
710                 parse_host_arg(&hi, line + len + 1, pktlen - len - 1);
711
712         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
713                 struct daemon_service *s = &(daemon_service[i]);
714                 const char *arg;
715
716                 if (skip_prefix(line, "git-", &arg) &&
717                     skip_prefix(arg, s->name, &arg) &&
718                     *arg++ == ' ') {
719                         /*
720                          * Note: The directory here is probably context sensitive,
721                          * and might depend on the actual service being performed.
722                          */
723                         int rc = run_service(arg, s, &hi);
724                         hostinfo_clear(&hi);
725                         return rc;
726                 }
727         }
728
729         hostinfo_clear(&hi);
730         logerror("Protocol error: '%s'", line);
731         return -1;
732 }
733
734 static int addrcmp(const struct sockaddr_storage *s1,
735     const struct sockaddr_storage *s2)
736 {
737         const struct sockaddr *sa1 = (const struct sockaddr*) s1;
738         const struct sockaddr *sa2 = (const struct sockaddr*) s2;
739
740         if (sa1->sa_family != sa2->sa_family)
741                 return sa1->sa_family - sa2->sa_family;
742         if (sa1->sa_family == AF_INET)
743                 return memcmp(&((struct sockaddr_in *)s1)->sin_addr,
744                     &((struct sockaddr_in *)s2)->sin_addr,
745                     sizeof(struct in_addr));
746 #ifndef NO_IPV6
747         if (sa1->sa_family == AF_INET6)
748                 return memcmp(&((struct sockaddr_in6 *)s1)->sin6_addr,
749                     &((struct sockaddr_in6 *)s2)->sin6_addr,
750                     sizeof(struct in6_addr));
751 #endif
752         return 0;
753 }
754
755 static int max_connections = 32;
756
757 static unsigned int live_children;
758
759 static struct child {
760         struct child *next;
761         struct child_process cld;
762         struct sockaddr_storage address;
763 } *firstborn;
764
765 static void add_child(struct child_process *cld, struct sockaddr *addr, socklen_t addrlen)
766 {
767         struct child *newborn, **cradle;
768
769         newborn = xcalloc(1, sizeof(*newborn));
770         live_children++;
771         memcpy(&newborn->cld, cld, sizeof(*cld));
772         memcpy(&newborn->address, addr, addrlen);
773         for (cradle = &firstborn; *cradle; cradle = &(*cradle)->next)
774                 if (!addrcmp(&(*cradle)->address, &newborn->address))
775                         break;
776         newborn->next = *cradle;
777         *cradle = newborn;
778 }
779
780 /*
781  * This gets called if the number of connections grows
782  * past "max_connections".
783  *
784  * We kill the newest connection from a duplicate IP.
785  */
786 static void kill_some_child(void)
787 {
788         const struct child *blanket, *next;
789
790         if (!(blanket = firstborn))
791                 return;
792
793         for (; (next = blanket->next); blanket = next)
794                 if (!addrcmp(&blanket->address, &next->address)) {
795                         kill(blanket->cld.pid, SIGTERM);
796                         break;
797                 }
798 }
799
800 static void check_dead_children(void)
801 {
802         int status;
803         pid_t pid;
804
805         struct child **cradle, *blanket;
806         for (cradle = &firstborn; (blanket = *cradle);)
807                 if ((pid = waitpid(blanket->cld.pid, &status, WNOHANG)) > 1) {
808                         const char *dead = "";
809                         if (status)
810                                 dead = " (with error)";
811                         loginfo("[%"PRIuMAX"] Disconnected%s", (uintmax_t)pid, dead);
812
813                         /* remove the child */
814                         *cradle = blanket->next;
815                         live_children--;
816                         child_process_clear(&blanket->cld);
817                         free(blanket);
818                 } else
819                         cradle = &blanket->next;
820 }
821
822 static struct argv_array cld_argv = ARGV_ARRAY_INIT;
823 static void handle(int incoming, struct sockaddr *addr, socklen_t addrlen)
824 {
825         struct child_process cld = CHILD_PROCESS_INIT;
826
827         if (max_connections && live_children >= max_connections) {
828                 kill_some_child();
829                 sleep(1);  /* give it some time to die */
830                 check_dead_children();
831                 if (live_children >= max_connections) {
832                         close(incoming);
833                         logerror("Too many children, dropping connection");
834                         return;
835                 }
836         }
837
838         if (addr->sa_family == AF_INET) {
839                 char buf[128] = "";
840                 struct sockaddr_in *sin_addr = (void *) addr;
841                 inet_ntop(addr->sa_family, &sin_addr->sin_addr, buf, sizeof(buf));
842                 argv_array_pushf(&cld.env_array, "REMOTE_ADDR=%s", buf);
843                 argv_array_pushf(&cld.env_array, "REMOTE_PORT=%d",
844                                  ntohs(sin_addr->sin_port));
845 #ifndef NO_IPV6
846         } else if (addr->sa_family == AF_INET6) {
847                 char buf[128] = "";
848                 struct sockaddr_in6 *sin6_addr = (void *) addr;
849                 inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(buf));
850                 argv_array_pushf(&cld.env_array, "REMOTE_ADDR=[%s]", buf);
851                 argv_array_pushf(&cld.env_array, "REMOTE_PORT=%d",
852                                  ntohs(sin6_addr->sin6_port));
853 #endif
854         }
855
856         cld.argv = cld_argv.argv;
857         cld.in = incoming;
858         cld.out = dup(incoming);
859
860         if (start_command(&cld))
861                 logerror("unable to fork");
862         else
863                 add_child(&cld, addr, addrlen);
864 }
865
866 static void child_handler(int signo)
867 {
868         /*
869          * Otherwise empty handler because systemcalls will get interrupted
870          * upon signal receipt
871          * SysV needs the handler to be rearmed
872          */
873         signal(SIGCHLD, child_handler);
874 }
875
876 static int set_reuse_addr(int sockfd)
877 {
878         int on = 1;
879
880         if (!reuseaddr)
881                 return 0;
882         return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
883                           &on, sizeof(on));
884 }
885
886 struct socketlist {
887         int *list;
888         size_t nr;
889         size_t alloc;
890 };
891
892 static const char *ip2str(int family, struct sockaddr *sin, socklen_t len)
893 {
894 #ifdef NO_IPV6
895         static char ip[INET_ADDRSTRLEN];
896 #else
897         static char ip[INET6_ADDRSTRLEN];
898 #endif
899
900         switch (family) {
901 #ifndef NO_IPV6
902         case AF_INET6:
903                 inet_ntop(family, &((struct sockaddr_in6*)sin)->sin6_addr, ip, len);
904                 break;
905 #endif
906         case AF_INET:
907                 inet_ntop(family, &((struct sockaddr_in*)sin)->sin_addr, ip, len);
908                 break;
909         default:
910                 xsnprintf(ip, sizeof(ip), "<unknown>");
911         }
912         return ip;
913 }
914
915 #ifndef NO_IPV6
916
917 static int setup_named_sock(char *listen_addr, int listen_port, struct socketlist *socklist)
918 {
919         int socknum = 0;
920         char pbuf[NI_MAXSERV];
921         struct addrinfo hints, *ai0, *ai;
922         int gai;
923         long flags;
924
925         xsnprintf(pbuf, sizeof(pbuf), "%d", listen_port);
926         memset(&hints, 0, sizeof(hints));
927         hints.ai_family = AF_UNSPEC;
928         hints.ai_socktype = SOCK_STREAM;
929         hints.ai_protocol = IPPROTO_TCP;
930         hints.ai_flags = AI_PASSIVE;
931
932         gai = getaddrinfo(listen_addr, pbuf, &hints, &ai0);
933         if (gai) {
934                 logerror("getaddrinfo() for %s failed: %s", listen_addr, gai_strerror(gai));
935                 return 0;
936         }
937
938         for (ai = ai0; ai; ai = ai->ai_next) {
939                 int sockfd;
940
941                 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
942                 if (sockfd < 0)
943                         continue;
944                 if (sockfd >= FD_SETSIZE) {
945                         logerror("Socket descriptor too large");
946                         close(sockfd);
947                         continue;
948                 }
949
950 #ifdef IPV6_V6ONLY
951                 if (ai->ai_family == AF_INET6) {
952                         int on = 1;
953                         setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
954                                    &on, sizeof(on));
955                         /* Note: error is not fatal */
956                 }
957 #endif
958
959                 if (set_reuse_addr(sockfd)) {
960                         logerror("Could not set SO_REUSEADDR: %s", strerror(errno));
961                         close(sockfd);
962                         continue;
963                 }
964
965                 set_keep_alive(sockfd);
966
967                 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
968                         logerror("Could not bind to %s: %s",
969                                  ip2str(ai->ai_family, ai->ai_addr, ai->ai_addrlen),
970                                  strerror(errno));
971                         close(sockfd);
972                         continue;       /* not fatal */
973                 }
974                 if (listen(sockfd, 5) < 0) {
975                         logerror("Could not listen to %s: %s",
976                                  ip2str(ai->ai_family, ai->ai_addr, ai->ai_addrlen),
977                                  strerror(errno));
978                         close(sockfd);
979                         continue;       /* not fatal */
980                 }
981
982                 flags = fcntl(sockfd, F_GETFD, 0);
983                 if (flags >= 0)
984                         fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);
985
986                 ALLOC_GROW(socklist->list, socklist->nr + 1, socklist->alloc);
987                 socklist->list[socklist->nr++] = sockfd;
988                 socknum++;
989         }
990
991         freeaddrinfo(ai0);
992
993         return socknum;
994 }
995
996 #else /* NO_IPV6 */
997
998 static int setup_named_sock(char *listen_addr, int listen_port, struct socketlist *socklist)
999 {
1000         struct sockaddr_in sin;
1001         int sockfd;
1002         long flags;
1003
1004         memset(&sin, 0, sizeof sin);
1005         sin.sin_family = AF_INET;
1006         sin.sin_port = htons(listen_port);
1007
1008         if (listen_addr) {
1009                 /* Well, host better be an IP address here. */
1010                 if (inet_pton(AF_INET, listen_addr, &sin.sin_addr.s_addr) <= 0)
1011                         return 0;
1012         } else {
1013                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
1014         }
1015
1016         sockfd = socket(AF_INET, SOCK_STREAM, 0);
1017         if (sockfd < 0)
1018                 return 0;
1019
1020         if (set_reuse_addr(sockfd)) {
1021                 logerror("Could not set SO_REUSEADDR: %s", strerror(errno));
1022                 close(sockfd);
1023                 return 0;
1024         }
1025
1026         set_keep_alive(sockfd);
1027
1028         if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
1029                 logerror("Could not bind to %s: %s",
1030                          ip2str(AF_INET, (struct sockaddr *)&sin, sizeof(sin)),
1031                          strerror(errno));
1032                 close(sockfd);
1033                 return 0;
1034         }
1035
1036         if (listen(sockfd, 5) < 0) {
1037                 logerror("Could not listen to %s: %s",
1038                          ip2str(AF_INET, (struct sockaddr *)&sin, sizeof(sin)),
1039                          strerror(errno));
1040                 close(sockfd);
1041                 return 0;
1042         }
1043
1044         flags = fcntl(sockfd, F_GETFD, 0);
1045         if (flags >= 0)
1046                 fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);
1047
1048         ALLOC_GROW(socklist->list, socklist->nr + 1, socklist->alloc);
1049         socklist->list[socklist->nr++] = sockfd;
1050         return 1;
1051 }
1052
1053 #endif
1054
1055 static void socksetup(struct string_list *listen_addr, int listen_port, struct socketlist *socklist)
1056 {
1057         if (!listen_addr->nr)
1058                 setup_named_sock(NULL, listen_port, socklist);
1059         else {
1060                 int i, socknum;
1061                 for (i = 0; i < listen_addr->nr; i++) {
1062                         socknum = setup_named_sock(listen_addr->items[i].string,
1063                                                    listen_port, socklist);
1064
1065                         if (socknum == 0)
1066                                 logerror("unable to allocate any listen sockets for host %s on port %u",
1067                                          listen_addr->items[i].string, listen_port);
1068                 }
1069         }
1070 }
1071
1072 static int service_loop(struct socketlist *socklist)
1073 {
1074         struct pollfd *pfd;
1075         int i;
1076
1077         pfd = xcalloc(socklist->nr, sizeof(struct pollfd));
1078
1079         for (i = 0; i < socklist->nr; i++) {
1080                 pfd[i].fd = socklist->list[i];
1081                 pfd[i].events = POLLIN;
1082         }
1083
1084         signal(SIGCHLD, child_handler);
1085
1086         for (;;) {
1087                 int i;
1088
1089                 check_dead_children();
1090
1091                 if (poll(pfd, socklist->nr, -1) < 0) {
1092                         if (errno != EINTR) {
1093                                 logerror("Poll failed, resuming: %s",
1094                                       strerror(errno));
1095                                 sleep(1);
1096                         }
1097                         continue;
1098                 }
1099
1100                 for (i = 0; i < socklist->nr; i++) {
1101                         if (pfd[i].revents & POLLIN) {
1102                                 union {
1103                                         struct sockaddr sa;
1104                                         struct sockaddr_in sai;
1105 #ifndef NO_IPV6
1106                                         struct sockaddr_in6 sai6;
1107 #endif
1108                                 } ss;
1109                                 socklen_t sslen = sizeof(ss);
1110                                 int incoming = accept(pfd[i].fd, &ss.sa, &sslen);
1111                                 if (incoming < 0) {
1112                                         switch (errno) {
1113                                         case EAGAIN:
1114                                         case EINTR:
1115                                         case ECONNABORTED:
1116                                                 continue;
1117                                         default:
1118                                                 die_errno("accept returned");
1119                                         }
1120                                 }
1121                                 handle(incoming, &ss.sa, sslen);
1122                         }
1123                 }
1124         }
1125 }
1126
1127 #ifdef NO_POSIX_GOODIES
1128
1129 struct credentials;
1130
1131 static void drop_privileges(struct credentials *cred)
1132 {
1133         /* nothing */
1134 }
1135
1136 static struct credentials *prepare_credentials(const char *user_name,
1137     const char *group_name)
1138 {
1139         die("--user not supported on this platform");
1140 }
1141
1142 #else
1143
1144 struct credentials {
1145         struct passwd *pass;
1146         gid_t gid;
1147 };
1148
1149 static void drop_privileges(struct credentials *cred)
1150 {
1151         if (cred && (initgroups(cred->pass->pw_name, cred->gid) ||
1152             setgid (cred->gid) || setuid(cred->pass->pw_uid)))
1153                 die("cannot drop privileges");
1154 }
1155
1156 static struct credentials *prepare_credentials(const char *user_name,
1157     const char *group_name)
1158 {
1159         static struct credentials c;
1160
1161         c.pass = getpwnam(user_name);
1162         if (!c.pass)
1163                 die("user not found - %s", user_name);
1164
1165         if (!group_name)
1166                 c.gid = c.pass->pw_gid;
1167         else {
1168                 struct group *group = getgrnam(group_name);
1169                 if (!group)
1170                         die("group not found - %s", group_name);
1171
1172                 c.gid = group->gr_gid;
1173         }
1174
1175         return &c;
1176 }
1177 #endif
1178
1179 static int serve(struct string_list *listen_addr, int listen_port,
1180     struct credentials *cred)
1181 {
1182         struct socketlist socklist = { NULL, 0, 0 };
1183
1184         socksetup(listen_addr, listen_port, &socklist);
1185         if (socklist.nr == 0)
1186                 die("unable to allocate any listen sockets on port %u",
1187                     listen_port);
1188
1189         drop_privileges(cred);
1190
1191         loginfo("Ready to rumble");
1192
1193         return service_loop(&socklist);
1194 }
1195
1196 int cmd_main(int argc, const char **argv)
1197 {
1198         int listen_port = 0;
1199         struct string_list listen_addr = STRING_LIST_INIT_NODUP;
1200         int serve_mode = 0, inetd_mode = 0;
1201         const char *pid_file = NULL, *user_name = NULL, *group_name = NULL;
1202         int detach = 0;
1203         struct credentials *cred = NULL;
1204         int i;
1205
1206         for (i = 1; i < argc; i++) {
1207                 const char *arg = argv[i];
1208                 const char *v;
1209
1210                 if (skip_prefix(arg, "--listen=", &v)) {
1211                         string_list_append(&listen_addr, xstrdup_tolower(v));
1212                         continue;
1213                 }
1214                 if (skip_prefix(arg, "--port=", &v)) {
1215                         char *end;
1216                         unsigned long n;
1217                         n = strtoul(v, &end, 0);
1218                         if (*v && !*end) {
1219                                 listen_port = n;
1220                                 continue;
1221                         }
1222                 }
1223                 if (!strcmp(arg, "--serve")) {
1224                         serve_mode = 1;
1225                         continue;
1226                 }
1227                 if (!strcmp(arg, "--inetd")) {
1228                         inetd_mode = 1;
1229                         log_syslog = 1;
1230                         continue;
1231                 }
1232                 if (!strcmp(arg, "--verbose")) {
1233                         verbose = 1;
1234                         continue;
1235                 }
1236                 if (!strcmp(arg, "--syslog")) {
1237                         log_syslog = 1;
1238                         continue;
1239                 }
1240                 if (!strcmp(arg, "--export-all")) {
1241                         export_all_trees = 1;
1242                         continue;
1243                 }
1244                 if (skip_prefix(arg, "--access-hook=", &v)) {
1245                         access_hook = v;
1246                         continue;
1247                 }
1248                 if (skip_prefix(arg, "--timeout=", &v)) {
1249                         timeout = atoi(v);
1250                         continue;
1251                 }
1252                 if (skip_prefix(arg, "--init-timeout=", &v)) {
1253                         init_timeout = atoi(v);
1254                         continue;
1255                 }
1256                 if (skip_prefix(arg, "--max-connections=", &v)) {
1257                         max_connections = atoi(v);
1258                         if (max_connections < 0)
1259                                 max_connections = 0;            /* unlimited */
1260                         continue;
1261                 }
1262                 if (!strcmp(arg, "--strict-paths")) {
1263                         strict_paths = 1;
1264                         continue;
1265                 }
1266                 if (skip_prefix(arg, "--base-path=", &v)) {
1267                         base_path = v;
1268                         continue;
1269                 }
1270                 if (!strcmp(arg, "--base-path-relaxed")) {
1271                         base_path_relaxed = 1;
1272                         continue;
1273                 }
1274                 if (skip_prefix(arg, "--interpolated-path=", &v)) {
1275                         interpolated_path = v;
1276                         continue;
1277                 }
1278                 if (!strcmp(arg, "--reuseaddr")) {
1279                         reuseaddr = 1;
1280                         continue;
1281                 }
1282                 if (!strcmp(arg, "--user-path")) {
1283                         user_path = "";
1284                         continue;
1285                 }
1286                 if (skip_prefix(arg, "--user-path=", &v)) {
1287                         user_path = v;
1288                         continue;
1289                 }
1290                 if (skip_prefix(arg, "--pid-file=", &v)) {
1291                         pid_file = v;
1292                         continue;
1293                 }
1294                 if (!strcmp(arg, "--detach")) {
1295                         detach = 1;
1296                         log_syslog = 1;
1297                         continue;
1298                 }
1299                 if (skip_prefix(arg, "--user=", &v)) {
1300                         user_name = v;
1301                         continue;
1302                 }
1303                 if (skip_prefix(arg, "--group=", &v)) {
1304                         group_name = v;
1305                         continue;
1306                 }
1307                 if (skip_prefix(arg, "--enable=", &v)) {
1308                         enable_service(v, 1);
1309                         continue;
1310                 }
1311                 if (skip_prefix(arg, "--disable=", &v)) {
1312                         enable_service(v, 0);
1313                         continue;
1314                 }
1315                 if (skip_prefix(arg, "--allow-override=", &v)) {
1316                         make_service_overridable(v, 1);
1317                         continue;
1318                 }
1319                 if (skip_prefix(arg, "--forbid-override=", &v)) {
1320                         make_service_overridable(v, 0);
1321                         continue;
1322                 }
1323                 if (!strcmp(arg, "--informative-errors")) {
1324                         informative_errors = 1;
1325                         continue;
1326                 }
1327                 if (!strcmp(arg, "--no-informative-errors")) {
1328                         informative_errors = 0;
1329                         continue;
1330                 }
1331                 if (!strcmp(arg, "--")) {
1332                         ok_paths = &argv[i+1];
1333                         break;
1334                 } else if (arg[0] != '-') {
1335                         ok_paths = &argv[i];
1336                         break;
1337                 }
1338
1339                 usage(daemon_usage);
1340         }
1341
1342         if (log_syslog) {
1343                 openlog("git-daemon", LOG_PID, LOG_DAEMON);
1344                 set_die_routine(daemon_die);
1345         } else
1346                 /* avoid splitting a message in the middle */
1347                 setvbuf(stderr, NULL, _IOFBF, 4096);
1348
1349         if (inetd_mode && (detach || group_name || user_name))
1350                 die("--detach, --user and --group are incompatible with --inetd");
1351
1352         if (inetd_mode && (listen_port || (listen_addr.nr > 0)))
1353                 die("--listen= and --port= are incompatible with --inetd");
1354         else if (listen_port == 0)
1355                 listen_port = DEFAULT_GIT_PORT;
1356
1357         if (group_name && !user_name)
1358                 die("--group supplied without --user");
1359
1360         if (user_name)
1361                 cred = prepare_credentials(user_name, group_name);
1362
1363         if (strict_paths && (!ok_paths || !*ok_paths))
1364                 die("option --strict-paths requires a whitelist");
1365
1366         if (base_path && !is_directory(base_path))
1367                 die("base-path '%s' does not exist or is not a directory",
1368                     base_path);
1369
1370         if (inetd_mode) {
1371                 if (!freopen("/dev/null", "w", stderr))
1372                         die_errno("failed to redirect stderr to /dev/null");
1373         }
1374
1375         if (inetd_mode || serve_mode)
1376                 return execute();
1377
1378         if (detach) {
1379                 if (daemonize())
1380                         die("--detach not supported on this platform");
1381         }
1382
1383         if (pid_file)
1384                 write_file(pid_file, "%"PRIuMAX, (uintmax_t) getpid());
1385
1386         /* prepare argv for serving-processes */
1387         argv_array_push(&cld_argv, argv[0]); /* git-daemon */
1388         argv_array_push(&cld_argv, "--serve");
1389         for (i = 1; i < argc; ++i)
1390                 argv_array_push(&cld_argv, argv[i]);
1391
1392         return serve(&listen_addr, listen_port, cred);
1393 }